<!DOCTYPE html>
<html>
    <head>
        <title>Example</title>
        <script>
            var toggleHidden = function(){
                var elem = document.getElementById("toggle");
                if(elem.hasAttribute("hidden")){
                    elem.removeAttribute("hidden");
                }else{
                    elem.setAttribute("hidden","hidden");
                }
            }
        </script>
    </head>
    <body>
<!-- hidden布尔属性,元素无需关注 -->
        <button onclick="toggleHidden()">Toggle</button>
        <table>
            <tr><th>Name</th><th>City</th></tr>
            <tr><td>Adam Freeman</td><td>London</td></tr>
            <tr id="toggle" hidden><td>Joe Smith</td><td>New York</td></tr>
            <tr><td>Anne Jones</td><td>Pairs</td></tr>
        </table>
    </body>
</html>